Electric field and strain engineering tuning of 2D Gr/α-Ga2O3 van der Waals heterostructures

Abstract

Functional electrical devices based on two-dimensional (2D) materials can benefit from the considerable potential of van der Waals heterostructures (vdWHs). We investigated the electrical characteristics, contact behavior, and optical performance of 2D metal-semiconductor vdWHs comprised of graphene and α-Ga₂O₃, in which α-Ga₂O₃ possesses two polarization states that are diametrically opposed to one another (α-Ga₂O₃↑ and α-Ga₂O₃↓). Utilizing first-principles calculations, Gr/α-Ga₂O₃↑ vdWHs have n-type Schottky contacts, while Gr/α-Ga₂O₃↓ vdWHs have n-type Ohmic contacts. Applying strains and electric fields efficiently regulates the band alignment between these two substances, which can reach different contact types. Moreover, our research findings suggest that vertical strains and electric fields can boost the carrier concentration in the Gr layer to about ∼10¹³ cm⁻². Besides, the Gr/α-Ga₂O₃ vdWHs have much higher optical absorption than the isolated α-Ga₂O₃ monolayers in the visible and UV spectral regions. Consequently, the fact that Gr/α-Ga₂O₃ vdWHs are capable of attaining controlled contact types makes them especially well-suited for use in applications involving electrical and optoelectronic devices.